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BACKGROUND
OHB-Sweden (previously Space Systems Division at SSC) has developed the Prisma system, Prototype Research Instruments and Space Mission technology Advancement, to demonstrate critical technologies for enabling various types of proximity operations: rendezvous, sustained formation flying, collision avoidance, etc. Prisma consists of two space vehicles, an agile Mango and a passive Tango that plays the role of a translationally passive resident space object (RSO). Launched as a single Combine on June 15, 2010, the system is now commissioned and well into the Nominal mission. The partners/experimentors in the current ongoing Basic mission are DLR, CNES and DTU.
Mango and Tango are, since August 11, separated and technology demonstrations are continuously in progress, with the Mango and Tango units playing different roles as the experiments proceed. Both Prisma units are 3-axis stabilized spacecraft, and Mango has monopropellant thrusters. Navigation-wise the Prisma system carries multiple sensors for space situational awareness. These include a differential GPS system for inter-satellite distances exceeding a few meters. A visual based sensor (VBS) system identifies the RSO (Tango) at distances up to several hundreds of kilometers, and tracks the pose of the target (Tango) down to as close as 0.1 meters.
OHB-Sweden (previously Space Systems Division at SSC) has a TAA in place with Princeton Satellite Systems (PSS) covering the areas of FF & RVD related guidance, navigation and control. The two companies are now looking to further develop the Prisma capabilities and possibilities in, primarily, the US. | INVITATION TO
USER EXPERIMENTS
After the Nominal mission, in late summer/autumn 2011, it is expected that the Mango spacecraft will have 50+ m/s of dV remaining. OHB-Sweden (previously Space Systems Division at SSC), in conjunction with Princeton Satellite Systems, have started to offer civilian and military organizations in the United States the opportunity to use Prisma for their own flight experiments.
This offer is now expanded and the invitation is opened also to non-US entities. User Experiments could in principle involve changes in the flight software via additions of own S/W modules. Example of areas for User Experiments: ground supported experiments, sensor data processing for situational awareness, autonomous operation formation flying and relative maneuvers, automated check out and planning, sensor experiments, inspection, servicing, repair and 3D proximity operations, etc | | PRISMA COPIES
TAILORED FOR USERS
OHB-Sweden (previously Space Systems Division at SSC) is also interested in building copies of Prisma for US and non-US organizations. These could be follow-ons to the experiments suggested above.
This would allow rapid advances in in-orbit technology through the use of a flight tested spacecraft. TRL raising and risk reduction are potential possibilities. Purchased Prisma spacecraft could be loaded with customer flight software and host new sensors. New spacecraft would be available within about 18 months (assuming a rebuild of current design).
OHB-Sweden (previously Space Systems Division at SSC) can provide interfaces to most standard launch vehicles. | 
PRISMA PRODUCT OPTIONS
The Prisma Testbed provides a number of different options for customers. Potential examples: | 1. | Time slots with tailored maneuvers - customers provide desired maneuvers (translational + rotational) which are executed by the Prisma operations team on the flying Prisma. This option is the fastest path to flight testing. Customer ground software can also be integrated into the Prisma ground support system to produce an automated ground loop. | | 2. | User S/W – User software, e.g Planning, GNC, autonomy related S/W, etc, is integrated into the overall onboard S/W of the flying Prisma. This software can be used to control the spacecraft. The telemetry data is collected and provided to the customer for evaluation. OHB-Sweden (previously Space Systems Division at SSC) and PSS would provide the support for integration of the user software.
| | 3. | Prisma Testbed - This option includes a complete Prisma spacecraft. The Prisma retains its flight processor and the original set of GNC proximity operations functionality thus providing a flight-tested backup to the customers software. In addition, on top of the nominal avionics, the system will/can be equipped with an electronics bay for the customer’s own flight computer and interfaces to the customer’s own sensors. Multiple customers can share the same flight computer if desired. The operations can be done by OHB-Sweden or by the customer themselves, in the latter case a full RAMSES control station will be part of the delivery. | | 4. | Prisma Testbed with Pre Loaded Flight Computer - This option includes the complete Prisma spacecraft plus a complete flight computer system based on the PowerPC 750 processor euipped with its own attitude and orbit control software. The customer can add their own software to this flight computer with support from the Prisma team. |  PRISMA – GENERAL SPECIFICATIONS
The figures below show the main layout of the two Prisma spacecraft – Mango and Tango, outlining also the major spacecraft GNC components.
Mango: The structure is a box made by standard aluminum honeycomb panels. Two body-fixed 1 m2 solar panels are deployed after separation from the launch vehicle, the power system is over-sized to allow Prox Ops in arbitrary geometry domains and approach vectors relative the RSO and for extended periods of time. The upper part of the S/C is configured such that the VBS cameras, one with long range and one with short range focus, have a clean view toward the RSO in the nominal flight configuration.
Tango is an aluminum honeycomb panel box with one side consisting of the body mounted solar array. The Tango is clamped to the Mango upper part during the launch via a small separation system developed by OHB-Sweden for previous projects. Tango is equipped with 2 sets of infrared LEDs for creating the cooperative mode of the VBS related experiments, one global omni-coverage set and one local set, with precise sub centimeter precision, for final approach / recede experiments in a narrow approach zone.
PRISMA - GNC SPECIFICATIONS
The core of the Avionics System on both spacecraft is a LEON 3 32-bit fault tolerant processor implemented in an Actel FPGA. Also TM/TC functions are implemented in FPGAs. The processor communicates with a 1 GB mass memory and the TM/TC functions via a SpaceWire bus, while the communication to the platform units electronics is based on the CAN bus. The Onboard Software (OBSW) application layer is to a large extent built in a MATLAB / Simulink (Mathworks) based environment where the source code is autocoded using Real Time Workshop/Embedded Coder. The development environment and methods used greatly simplify the implementation of the GNC software which of course also is developed in MATLAB / Simulink. The Prisma testbed comes with a flight proven set of GNC capabilities for various types of proximity operations: GPS based and VBS based rendezvous, sustained formation flying, T-periodic relative motion for a variety of geometries, safe orbit guidance and collision avoidance. 
FOR MORE INFORMATION
| For non-US organisations: | For US organisations: | Technical Point of Contact:
Bjorn Jakobsson
OHB-Sweden
AOCS department
Solna Strandväg 86,
SE-17122 Solna, Sweden
Phone: +46 8 627 64 40
Email:
bjorn.jakobsson@ohb-sweden.se
www.ohb-sweden.se | Commercial Point of Contact:
Bengt Larsson
OHB-Sweden
Business Department
Solna Strandväg 86,
SE-17122 Solna, Sweden
Phone: +46 8 627 64 40
Email: bengt.larsson@ohb-sweden.se
www.ohb-sweden.se | Michael Paluszek Princeton Satellite Systems, Inc. 6 Market Street, Suite 926 Plainsboro, NJ 08536, USA Phone: +1 609 275 9606 Fax: +1 609 275 9609 Email: map@psatellite.com www.psatellite.com | |